Radio apparatus

ABSTRACT

A radio apparatus comprising: a first transceiver means arranged to receive and transmit packets according to a first protocol; a second transceiver means arranged to receive or transmit packets according to a second, different protocol, the second transceiver means being located such that interference is possible between packets of the first and second protocols; analyzing means for determining a probability that a packet to be transmitted or received by the first transceiver means does not contain only redundant information; and decision means for making a decision based on the determined probability as to whether or not the packet should be respectively transmitted or received. The first transceiver means is arranged to respectively transmit or receive the packet or not according to the decision.

This invention relates to radio apparatus capable of operating in aradio communications system and in particular to such a radio when in aninterference situation with another radio.

Laptop computers and other portable devices such as mobile telephonesand PDAs (personal digital assistants) are now commonly equipped withradio transceivers that allow them to be connected to a communicationsnetwork, for example via wireless local area network (WLAN) accesspoints or base stations, for the transfer of data. One example of a setof commonly used wireless network standards is the IEEE 802.11 system.In such a system access points are provided at fixed locations. Otherdevices can connect by radio to an access point and thereby transmit andreceive data to and from a network to which the access point isconnected. Typically, the access point will be connected to theinternet.

Such devices are capable of carrying out multiple functions. Forexample, a mobile telephone might be capable of downloading music andringtones from the internet to be stored and subsequently played andhave an in-built camera and video recorder, in addition to its usualvoice and message communications capabilities. A laptop computer cancarry out all the functions of a standard PC and could also be providedwith VoIP (Voice over Internet Protocol) capabilities. Typically a PDAprovides combined computing and telecommunications functions. Thesedevices are designed with a computer architecture including a centralprocessing unit (CPU) controlling other modules such as the camera, dataand voice transceivers and various memories.

It is common for devices of the type discussed above to be provided withthe capability to operate according to another protocol, for example ina short range frequency-hopping radio system such as Bluetooth, as wellas being able to connect to a WLAN. This enables the device to carry outmultiple functions simultaneously, for example to be downloading data,whilst being in a telephone call via a headset. In order to be capableof operation within both systems, such a device must be provided withboth an IEEE 802.11 radio and a Bluetooth radio. When both types ofradio are provided in a single device the radios are said to becollocated and are capable of interfering with each other. Interferencecan also occur between an IEEE 802.11 radio in one device and aBluetooth radio in another device when the two devices happen to bebrought into close physical proximity e.g. if an active user of aWLAN-enabled laptop has a telephone conversation on his or her mobiletelephone through a Bluetooth headset.

Both IEEE 802.11 and Bluetooth operate in the 2.4 GHz ISM (industrial,scientific, and medical) frequency band. IEEE 802.11 has a signallingmethod which uses modulation techniques known as DSSS (Direct SequenceSpread Spectrum) and OFDM (Orthogonal Frequency Division Multiplexing).By contrast, the Bluetooth system uses FHSS (Frequency Hopping SpreadSpectrum) including AFH (Adaptive Frequency Hopping) which allows it toavoid using crowded frequencies. The choice of modulation technique usedin the two standards reflects the different intended purposes of the twosystems, Bluetooth being designed to be cheap and robust whereasthroughput being an important factor in the IEEE 802.11 system. Althoughthe two systems operate in the same ISM frequency band their differentmultiplexing schemes employing the different modulation techniquesminimise interference in general use. However, when Bluetooth and IEEE802.11 radios are collocated or in close proximity such that, forexample, there is insufficient isolation between the two radios or theyshare an antenna via a switch, even though the two systems may usenon-overlapping frequencies, the IEEE 802.11 data throughput isseriously degraded by Bluetooth voice links. In the Bluetooth radiosystem, frequency hopping is performed for 79 channels 1 MHz wide in therange from 2402 to 2480 MHz central channel frequency, or if AFH isused, any number of channels between 20 and 79. Within the 2.4 GHz ISMband the IEEE 802.11 system allocates up to 14 channels, typically 22MHz wide, with centre channel frequencies from 2412 to 2484 MHz.Therefore, a transceiver of IEEE 802.11 signals can interfere with orsuffer interference from some of the Bluetooth channels. This isespecially true in certain circumstances.

Examples of the circumstances when interference is problematic betweenIEEE 802.11 and Bluetooth radios are when a single antenna is sharedbetween the two radios (which would happen if the two radios areprovided in the same device and there are severe space constraints),when data is being predominantly transferred from a remote access pointto the local IEEE 802.11 radio (e.g. downloads from the internet, theWLAN base station being the remote access point), when the IEEE 802.11received signal strength is low, and when long IEEE 802.11 data packetsare being used. It is data reception to the IEEE 802.11 radio thatsuffers in such circumstances for various reasons, including

-   -   Bluetooth concentrates the energy in a narrower band so all of        the Bluetooth power will be within the IEEE 802.11 receive        filter, but only a small proportion of the IEEE 802.11 power        will be within the Bluetooth receive filter.    -   Most arbitration schemes will give priority to Bluetooth voice        over all other traffic, so (especially if an antenna is being        switched) IEEE 802.11 will suffer as a result.    -   Successful data transfer on IEEE 802.11 requires an ACK to be        transmitted back to the WLAN Access Point (AP), but this is        likely to be blocked by any arbitration scheme during Bluetooth        voice packets. Data or Management packet transmissions by the        collocated IEEE 802.11 transceiver can be scheduled to fit in        the gap between Synchronous Connection Orientated (SCO) packets        of the Bluetooth voice, but the downlink from the access point        is typically asynchronous and uncoordinated.

The interference means that transmissions of packets by a Bluetoothradio are likely to prevent reception of packets from an access point bythe IEEE 802.11 radio. This will be the case if a single antenna isswitched between the two radios, two separate antennas are used or asingle antenna is shared via a splitter. It will tend particularly tohappen at extremes of range of the radio protocol that is being receivedby the device: in this example IEEE 802.11. This is especiallyproblematic because IEEE 802.11 downlinks from the access point aretypically unsynchronised to the Bluetooth activity (as noted above).

Any errors in the IEEE 802.11 signals are treated in accordance with theprotocol. Thus if the IEEE 802.11 radio fails to receive a data packetcorrectly, two actions may be taken by the remote access point becauseit has failed to receive an acknowledgement. Firstly, the remote accesspoint attempts to resend the data at a lower data rate by (i) increasingthe amount of Forward Error Correction (FEC), (ii) reducing the numberof bits encoded per symbol and (iii) reducing the symbol rate. Anycombination of (i), (ii) and (iii) can be used, often only one or two ofthe techniques being used. Secondly, the remote access point waits sometime before re-sending the data, and each time sending fails, it waitslonger before attempting re-transmission. More specifically the IEEE802.11 remote access point uses contention-based access to the wirelessmedium, selecting a random time to attempt transmission within aback-off window and only transmitting if it does not detect anotherdevice starting a transmission earlier. There is a finite probabilitythat the remote access point and another device may select exactly thesame time to transmit which could be a reason for the packet not havingreached the IEEE 802.11 radio. Each time a re-transmission is made, thesize of the back-off window is doubled (up to a limit). The combinationof all these effects results in a “death spiral” of reduced IEEE 802.11throughput.

It is also possible for the interference to work the other way aroundsuch that the Bluetooth packets suffer interference as well as creatinginterference when other radio protocols are active.

Coexistence schemes which aim to minimise interference betweencollocated radios are in use. One example of such a scheme is given inIEEE 802.15.2-2003 section 6 which uses Packet Traffic Arbitration(PTA). Requests from both radios are received at the PTA unit whichauthorises transmission and reception of messages. If two requests arereceived for simultaneous activity, the PTA unit predicts whether one orboth requests are likely to suffer interference in view of the other andthen allows or denies one of the requests as appropriate. Implementationof this scheme and other similar schemes depends on the RF design of theproduct, for example whether a single antenna is switched between thetwo radios or whether some degree of simultaneous operation is possibleby use of multiple antennas or a coupler/splitter. Operation of such ascheme can be enhanced by use of power save modes e.g. use of IEEE802.11 power-save to schedule downlink traffic between Bluetooth SCOslots. However, such coexistence schemes are often unsatisfactory forvarious reasons. One reason is that the remote transmitter from which adenied signal has been received does not know that arbitration is beingperformed at the device. Consequently the remote transmitter can notdistinguish between failure to deliver a packet due to an arbitrationdecision and failure due to poor channel conditions. The remotetransmitter will attempt re-transmission as previously explainedregardless of the reason for failure, even though re-transmission may bepointless in view of arbitration. Thus network resources are usedunnecessarily and further interference may result. Another reason isthat preventing full simultaneous operation of both radios reduces theproportion of time that the wireless medium can be used and hencereduces maximum throughput. A further reason is that significant delaycan be suffered by a message whose request has been denied andconsequently performance and reliability are affected.

It would be desirable to mitigate interference between a radio whichcould interfere with another radio operating under another radioprotocol whilst minimising performance degradation.

According to a first aspect of the present invention, there is provideda radio apparatus comprising: a first transceiver means arranged toreceive and transmit packets according to a first protocol ; a secondtransceiver means arranged to receive or transmit packets according to asecond, different protocol, the second transceiver means being locatedsuch that interference is possible between packets of the first andsecond protocols; analysing means for determining a probability that apacket to be transmitted or received by the first transceiver means doesnot contain only redundant information; and decision means for making adecision based on the determined probability as to whether or not thepacket should be respectively transmitted or received, wherein the firsttransceiver means is arranged to respectively transmit or receive thepacket or not according to the decision.

According to a second aspect of the present invention, there is provideda method of reducing interference between a first and a secondtransceiver located in a radio apparatus, the first transceiver beingoperable to receive and transmit packets according to a first protocoland the second transceiver being operable to receive or transmit packetsaccording to a second, different protocol, the method comprising thesteps of: determining a probability that a packet to be transmitted orreceived by the first radio apparatus does not contain only redundantinformation; making a decision based on the determined probability as towhether or not the packet should be respectively transmitted orreceived; and respectively transmitting or receiving the packet or notaccording to the decision.

In the Bluetooth system, devices are categorised as being “master” or“slave” devices. One master device can have a point-to-point connectionwith up to seven slave devices, thus forming a piconet. The standardBluetooth protocol dictates that voice packets are transmitted between amaster and slave at strictly regular intervals under the SynchronousConnection Orientated (SCO) protocol, regardless of content. There maybe a maximum of three SCO links within a piconet. The master device isset up to reserve slots periodically and thus packets are transmitted atregular intervals. This continues for the entire duration of the SCOlink. This duration is defined as starting either when the call isrequested or when the user starts to use the Bluetooth headset. The endof the duration is defined as when the user stops using the Bluetoothheadset or the call ends. Bluetooth also uses the extended SCO (eSCO)protocol which also has strictly periodic reserved slots but may alsohave a limited number of re-transmission slots following the reservedslots.

In telephony applications, voice data has the characteristic that (in aparticular direction) there are significant and regular gaps of silence.This means that during an active call, for example in a packet-basedsystem, there will be many packets transmitted that do not contain anyproper voice data but rather only contain redundant informationincluding background noise. Such packets are nevertheless capable ofinterfering with an IEEE 802.11 radio situated in close enough proximityfor interference to be a problem.

It can therefore be understood that the various aspects of the inventionare advantageous because they enable a radio such as a Bluetooth radioto change its behaviour as compared to a standard protocol to reduce thenumber of voice packets being transmitted during a call. If fewerpackets are transmitted, the likelihood of interference with anotherradio in close proximity is reduced. Even though interference with theother radio is reduced, the radio such as a Bluetooth radio would notsuffer a significant degradation to its voice link. By preferentiallyselecting certain packets not to be transmitted based on whether theycontain voice data or only redundant information, intelligibility ofspeech can nevertheless be maintained. Such preferential selection canalso be used to select certain packets not to be received, as will beexplained in more detail below.

The various aspects of the invention are similarly advantageous withrespect to transmission of other information packets such as data ornon-voice audio packets. Although such transmission may not contain asmany packets not carrying information except redundant data, there arenevertheless likely to be gaps in transmission of non-redundant data.Thus the invention is also applicable to non-voice data such asnon-voice audio packets and video.

It can be understood that the term “redundant” information comprisesvarious types of information in dependence on the application. Forexample, when implementing the invention for voice packets, anybackground noise could be considered to be redundant information becauseit distracts from the speech. Thus background noise could take variousforms such as traffic noise and speech other than that from the usersand could include background audio in this case. On the other hand, ifthe invention is being implemented for non-voice audio packets, allnon-silent audio data including music and sound-effects would benon-redundant. Thus any information that is unnecessary or superfluousto the particular application is considered to be redundant.

The invention has the further advantage of saving power in the device,because if fewer packets are transmitted, less total energy istransmitted.

The invention will now be described, by way of example, with referenceto the accompanying drawing, in which:

FIG. 1 shows a mobile telephone, its associated headset, a furthermobile telephone and a WLAN access point for use in embodiments of theinvention.

In the FIGURE, like reference numerals indicate like parts.

FIG. 1 shows an example of a situation in which interference can occurbetween two radio systems of different types. In this embodiment thefirst radio system comprises a pair of Bluetooth radios and the secondradio system of a different type comprises an IEEE 802.11 radioassociated with an IEEE 802.11 Wireless Local Area Network (WLAN) accesspoint.

In the FIGURE there is shown a mobile telephone (handset) 1 and itsassociated headset 2. There is also an IEEE 802.11 Access Point (AP) 4,which as well as providing a local network access point also provides agateway to the internet for devices within its range. Although in theFIGURE only the handset 1 (and the headset 2) are within range of the AP4, in practice the AP 4 can serve many devices simultaneously. Wirelessconnections are shown with dotted lines. Thus there is a wirelessconnection 8 between the handset 1 and the headset 2. There is awireless connection 10 between the handset 1 and the AP 4.

In FIG. 1 there is further shown another mobile telephone handset 24. Toavoid complicating the following description, the handset 24 is assumedto be remote to the other components, but it could be within range ofthe AP 4. In this embodiment the handset 1 and the other handset 24 arecapable of wireless communication with each other in accordance with acellular protocol, and the handset 1 can undertake such a call inconjunction with the headset 2. It will be appreciated that the twohandsets could alternatively communicate using a VoIP protocol via theAP 4.

In operation, various interference situations can arise as a result ofthe close proximity of two radios. One example is that the handset 1could be downloading data from the internet through the AP 4 while beingin an active telephone call using the headset 2. In order to be able tocarry out both of these actions, the handset 1 is provided with both anIEEE 802.11 radio and a Bluetooth radio. Thus interference could occurbetween these two radios. The headset 2 is also provided with aBluetooth radio. Thus interference with the IEEE 802.11 radio couldoccur with the Bluetooth radio within the handset 1 as a result ofBluetooth signals between the headset 2 and the handset 1.

The situation of the mobile telephone downloading data via the AP 4 andbeing in an active telephone call with the other handset 24 using theheadset 2 is now considered in more detail.

The wireless connection 10 between the handset 1 and the AP 4 is shownas bi-directional, a first connection 10 a representing transmissionsfrom the handset 1 to the AP 4 and a second connection 10 b representingtransmissions from the AP 4 to the handset 1. The handset 1 has anaerial 30 through which wireless signals are transmitted and received.In this embodiment the aerial 30 is shared between the IEEE 802.11 andBluetooth radios of the device, by means of a splitter as known in theart.

The handset 1 comprises an IEEE 802.11 radio 40 and a Bluetooth radio60. In the FIGURE, the handset 1 is shown to be divided by a chainedline into left and right portions, the left portion being the IEEE802.11 radio 40 and the right portion being the Bluetooth radio 60. TheIEEE 802.11 and Bluetooth radios are not completely independent but arelinked in various ways. The IEEE radio 40 includes a Voice over IP(VoIP) application 44 and a data processing unit 46 whilst the Bluetoothradio 60 includes a voice processing unit 64 and a data processing unit66. Firstly, voice data can pass via the connection 34 between the VoIPapplication 44 of the IEEE 802.11 radio and the voice processing unit 64of the Bluetooth radio 60. Secondly, data transfer can occur between thetwo data processing units 46 and 66 via a connection 35.

Also shown in the handset 1 are two transceivers. In the IEEE 802.11radio 40 there is a transceiver 42 for transmitting and receivingexternal signals and messages via the aerial 30 to the AP 4. In theBluetooth section 60 there is a transceiver 62 for transmitting andreceiving signals and messages via the aerial 30 with the headset 2. Thetransceivers 42, 62 are shown in the FIGURE to be at the top of thehandset 1 proximate to the aerial 30. Both transceivers 42, 62 arearranged to be connected to various other modules of the handset 1. Forexample, the IEEE 802.11 transceiver 42 is connected to the VoIPapplication 44 and the data processing unit 46. Similarly, the Bluetoothtransceiver 62 is connected to the voice processing unit 64 and the dataprocessing unit 66. It will be appreciated by those skilled in the artthat the transceivers comprise receiving and transmitting means whichare used respectively for receiving incoming packets and transmittingoutgoing packets.

Further, there is shown a central arbitration unit 32 in the handset 1.This is common to both sections of the handset 1 and is connected toboth the transceivers 42, 62. It could in practice form a part of acontroller of the handset 1. It is connected to all four of the voiceand data modules 44, 46, 64, 66 discussed above. Its purpose is toallocate priorities for receiving and/or transmission to incoming andoutgoing voice and data information packets.

In the Bluetooth section 60 there is an additional component denoted byreference numeral 68, which is a Voice Activity Detection (VAD) unit.This VAD unit 68 is arranged to be connected to the Bluetoothtransceiver 62, the central arbitration unit 32 and the Bluetooth voiceprocessing unit 64. This unit is capable of analysing packets of voicedata and thereby determining whether a packet contains actual voice dataor whether it merely contains background noise. This unit also comprisessome logic for requesting the central arbitration unit 32 to allowcertain action to be taken with respect to voice packets, as will beexplained in more detail below.

It will be understood by those skilled in the art that a handset capableof operating in both the IEEE 802.11 and Bluetooth systems would inpractice have many more modules arranged to include a protocol stack.FIG. 1 is intended to illustrate schematically a small number of thefunctional features of such a handset for the purpose of enabling abetter understanding of embodiments of the invention. In practice theremay not be such a clear-cut division between the IEEE 802.11 andBluetooth radios and the components as shown. In particular the centralarbitration unit 32 and the VAD unit 68 may be provided within a singlemodule which also comprises control and processing functions and thiscould be part of the same module as the Bluetooth transceiver 62.Furthermore, the embodiment described below where the handset 1 isdownloading data does not make use of the VoIP components in thehandset. These components are not essential but if present could be usedin embodiments of the invention.

FIG. 1 also shows schematically the headset 2. The headset 2 comprises atransceiver 3, connected to a VAD unit 5. There is an aerial 11 viawhich the transceiver 3 transmits and receives signals. The headset isalso provided with a speaker 7 and a microphone 9. The speaker 7 and themicrophone 9 are both connected to the transceiver 3 through the VADunit 5. It will be appreciated by those skilled in the art that thelayout of components of the headset 2 could vary and that othercomponents may be present in the headset 2. In particular the VAD unit 5could be provided as part of a control and processing module and thismodule could incorporate the transceiver 3.

The wireless connection 8 between the handset 1 and the headset 2 isshown as bi-directional, a first connection 8 a representingtransmissions from the handset 1 to the headset 2 and a secondconnection 8 b representing transmissions from the headset 2 to thehandset 1.

Similarly, the other handset 24 of FIG. 1 is shown, with abi-directional wireless connection 13 to the handset 1. A firstconnection 13 a represents transmissions from the handset 1 to the otherhandset 24 and a second connection 13 b represents transmissions fromthe other handset 24 to the handset 1. The wireless connection 13 showsschematically communications between the handset 1 and the other handset24, which are carried out in accordance with a mobile telephone networkprotocol as known in the art. Similar communication would occur withother handsets not located within access range of the AP 4. Examples ofsuch network protocols are cellular protocols (e.g. GSM, CDMA, UMTS). Inpractice such communications would occur via at least one networkelement such as a base station and/or base station controller, but suchelements are omitted from FIG. 1 for clarity. The handset 1 may havesome extra components for handling such communications but these are notshown in FIG. 1. Equally it will be appreciated that if the otherhandset 24 were within the range of the AP 4, the handset 1 and theother handset 24 could communicate using VoIP accessed by the IEEE802.11 transceiver 40.

In operation, various communications are carried out in the air spacebetween the two handsets 1, 24, the headset 2 and the AP 4. The wirelessconnection 10 shows communications between the handset 1 and the AP 4 inaccordance with the IEEE 802.11 standard protocol. This standardprotocol defines various features of transmission, such as the format ofcontrol signals, standard packet format and size, the transmissionfrequency, the length of each data burst and so on. The protocol alsodefines other features which affect how data is processed in the handset1 such as error checking and correction, registration of users,connections between users etc. Both messages and control signals aretransmitted. Messages are segmented into packets or frames prior tobeing transmitted. These packets or frames can carry information ofvarious types e.g. video data, voice data, text, files etc.

Similarly the wireless connection 8 shows communications between thehandset 1 and the headset 2 in accordance with the standard Bluetoothprotocol. Part of the Bluetooth protocol defines how non-voice data istransmitted. Another part of this protocol defines how voice data istransmitted in accordance with the Synchronous Connection Orientatedprotocol. In the SCO protocol, once there is an active voice connectionbetween two devices such as the handset 1 and the headset 2, a pair oftwo consecutive time slots, one in the uplink (handset to headset) andthe other in the downlink (headset to handset) are reserved at fixedintervals. Thus voice data is transmitted at regular intervals in bothdirections as long as the connection is active. So according to the SCOprotocol voice data is transmitted in this manner for the entire timethat a user of the handset 1 and headset 2 is engaged in a telephonecall using the headset 2.

As previously mentioned, the regular transmission of voice data inaccordance with the Bluetooth protocol as described above gives rise tomany “empty” voice data packets which do not contain any voice data butcontain only redundant information including background noise. This isbecause during a telephone conversation, usually only one person isspeaking at any one time and also because of pauses in an individual'sspeech. For example if the user of the handset 1 is speaking into theheadset 2, voice data is picked up at the microphone 9, processed intovoice packets in the transceiver 3 and then sent out via the aerial 11of the headset 2 across the wireless connection 8 b to the aerial 30 ofthe handset 1. The packets are sent in accordance with the Bluetoothprotocol at regular intervals in one slot of each pair of allocated timeslots as described above. Once received by the handset 1 they areprocessed and sent onto the other handset 24. Such packets containactual wanted voice data. In other words such packets containnon-redundant information.

However, during the same time period, in the others of the pairs ofallocated time slots, packets are transmitted from the handset 1 to theheadset 2 across the wireless connection 8 a. These packets areeffectively empty, containing only background noise and other redundantinformation because the user of the other handset 24 is not speaking.

Similarly, when the user of the other handset 24 is speaking, voicepackets are received at the handset 1 from the handset 24 across thewireless connection 13 b, processed and then transmitted in accordancewith the Bluetooth protocol from the handset 1 to the headset 2 acrossthe wireless connection 8 a for the user of the handset 1 to hear. Thesepackets contain voice data i.e. non-redundant information. However,during the same time, packets continue to be transmitted from theheadset 2 to the handset 1 across the wireless connection 8 b. Thesepackets are effectively empty, containing only background noise andother redundant information because the user of the handset 1 andheadset 2 is not speaking.

Since “empty” packets are capable of causing interference with the IEEE802.11 radio 40 of the handset 1, embodiments of the invention seek toreduce the number of such packets transmitted, to thereby reduce thelevel of interference, as will now be explained. The invention is alsoused to reduce the number of other packets being transmitted andreceived as appropriate to reduce interference for the benefit ofseveral devices.

Embodiments of the invention use Voice Activity Detection (VAD) orSilence Suppression to avoid transmitting unnecessary packets andthereby reduce the level of interference between the Bluetooth andnearby IEEE 802.11 radios. This technique can be used to mitigate boththe interference generated by the Bluetooth radio and, when combinedwith some arbitration logic, the interference suffered by the Bluetoothradio. By not sending some of the standard Bluetooth protocol voicepackets, the time for which the IEEE 802.11 receiver is blocked isreduced, thereby increasing throughput.

The VAD unit 68 operates using one of the following signal processingtechniques or more than one in combination to detect the presence ofvoice data:

-   -   Peak energy; Minimum energy; Prediction gain; Average normalized        squared pitch correlation; Spectral non-stationarity.

The techniques employed by the VAD unit 68 are not of course limited tothe above but any suitable voice detection technique can be used. Inthis embodiment these techniques are used in conjunction with one ormore criteria defining what constitutes non-redundant information andspecifically voice data and what constitutes only non-redundantinformation or background noise. These criteria are stored in a memoryforming part of or associated with the VAD unit 68, which as previouslyexplained could all be provided as part of a control and processing unitof which the VAD unit 68 (and possibly the central arbitration unit 32)forms a part. Thus the VAD unit 68 analyses the content of the packet ascompared to the stored criteria. The VAD unit 68 can thus determinewhether or not a packet contains voice data by detection of voice datain the packet and by means of the stored criteria. It will beappreciated that storing of criteria is not the only means by which theanalysis could be conducted.

An embodiment of the invention can be applied to the handset 1 ofFIG. 1. The handset 1 in this embodiment comprises the centralarbitration unit 32 which arbitrates between requests for receiving andtransmission of voice data by the Bluetooth radio 60 and data receivedfrom or transmitted to the AP 4 for the IEEE 802.11 radio 40.

When a user of the handset 1 and headset 2 connects into an active callusing the headset 2, voice data packets begin to be created in thehandset 1 and the headset 2. If the handset 1 and headset 2 werestandard ones in accordance with the prior art, these packets would betransmitted at regular intervals in accordance with the Bluetoothprotocol between the handset 1 via the aerial 30 and the headset 2across the wireless connection 8 as previously described. In thisembodiment the active call is with the other handset 24 and thereforepackets in accordance with a cellular protocol are also received andsent over the cellular link 13 between the handset 1 and the headset 24(via network elements as previously explained). The handset 1 differsfrom a standard handset in that in addition to sending voice packetsreceived from the other handset 24 directly to a voice data processingunit such as the voice data processing unit 64 in FIG. 1, all receivedvoice data packets are sent to the VAD unit 68. Thus for the duration ofthe active call, the VAD unit 68 detects whether or not voice data isarriving from the other handset 24 via the aerial 30. This can be donein conjunction with stored criteria as will be explained below. If theuser of the other handset 24 is speaking, voice data is incoming to thehandset 1 and is picked up at the aerial 30 and sent to the VAD unit 68which thereby knows that actual voice data is present.

The handset 1 further differs from standard handsets in that itcomprises the central arbitration unit 32. In the situation where theuser of the other handset 24 is not speaking, the VAD unit 68 determinesthat there is no actual voice data incoming to the handset 1 from theother handset 24. It is able to do this because the voice data ispassed, after some processing by cellular components of the handset 1(not shown), to the VAD unit 68. In this situation, the VAD unit 68requests the central arbitration unit 32 to disallow the sending ofBluetooth voice data packets out from the handset 1 to the headset 2.This request is made because if there is no actual voice data to be sentto the headset for the user of the handset 1 and headset 2 to hear, suchpackets will be effectively “empty” containing only background noise.Upon receiving this request, the central arbitration unit can decide toallocate a low priority to outgoing Bluetooth voice packets and toallocate a higher priority to IEEE 802.11 packets incoming to oroutgoing from the IEEE 802.11 transceiver 42 if appropriate. This wouldmean, for example, that if the user of the handset 1 was downloading forexample a video from the AP 4, this could be given a higher prioritythan outgoing Bluetooth voice packets, thereby reducing disruption tothe downloading process. In this case, if the aerial 30 had previouslybeen switched to receive Bluetooth packets, it would be instructed toswitch to receiving IEEE 802.11 packets.

In this situation i.e. when the user of the other handset 24 is notspeaking, it is likely that Bluetooth packets would still need to bereceived from the headset 2 at the handset 1 at regular intervalsbecause the user of the handset 1 is likely to be speaking and his orher speech would be picked up at the microphone 9 and therebytransmitted in packets to the handset 1. Thus a high priority is givento packets incoming from the headset 2 at this time.

In the situation where incoming voice data is present because the userof the other handset 24 is speaking, the VAD unit 68 requests thecentral arbitration unit 32 to allow voice data packets to be sent outof the handset 1 to the headset 2 for the user of the handset 1 andheadset 2 to hear. Upon receiving the request, the central arbitrationunit makes a decision that the packets should be transmitted andtherefore allocates a high priority to the voice data packets. The voicedata is passed, after some processing by cellular components of thehandset 1 (not shown), to the voice data processing unit 64. The voicedata processing unit 64 carries out various processing steps on the datasuch as checking for errors and then the voice data is segmented intovoice data packets and then passed to the VAD unit 68. The segmenteddata is then sent out from the transceiver 62 to the headset 2 acrossthe wireless connection 8 a.

The handset 1 is arranged to have a further refinement in theabove-described situation i.e. when the user of the other handset 24 isspeaking. Although voice data packets would in a standard system beincoming from the headset 2 to the handset 1 at regular intervals, it islikely that the user of the handset 1 is not speaking and consequently,voice packets being transmitted from the headset 2 to the handset 1 (forsubsequent transmission to the user of the other handset 24) will beempty packets containing only background noise. In other words, theprobability that these packets contain actual voice data is low. Thus onthis assumption the VAD unit 68 requests the central arbitration unit 32to allocate a low priority to receiving Bluetooth packets from theheadset 2. Upon receiving this request, the central arbitration unit 32can decide to allocate a low priority to such packets and instruct thetransceiver 62 to cease reception of Bluetooth packets from the headset2. Consequently, interference with any IEEE 802.11 activity is reduced.This would mean, for example, that if the user of the handset 1 wasdownloading for example a video from the AP 4, this could be given ahigher priority than incoming Bluetooth voice packets, thereby reducingdisruption to the downloading process.

It will be appreciated that this further refinement makes the assumptionthat the user of the handset 1 is not speaking when the user of thehandset 24 is speaking. Thus when the further refinement is implemented,the user of the handset 1 can not “speak over” the user of the handset24. However, implementation in this manner is of benefit to the IEEE802.11 radio 40.

It will be appreciated that the handset 24 or the cellular network inwhich it operates could also be implementing a voice detection system,possibly in accordance with or similar to embodiments of the presentinvention. If this is the case, there may be periods during which novoice packets are received at all at the handset 1. Thus the VAD unit 68can determine that there is no actual voice data incoming from packetsreceived over the cellular network either by analysis of incomingpackets or by the absence of incoming packets.

In a standard handset and headset arrangement, during an active call thehandset would continually receive voice packets from the headset 2, someof which would contain only background noise. Even if the handset 1 wereused with a standard headset, this embodiment would be applied to voicedata packets incoming from the headset. As can be seen in FIG. 1, theheadset 2 differs from a standard Bluetooth headset in that it comprisesthe VAD unit 5 and in that the transceiver 3 is modified from a standardtransceiver. Thus the headset 2 could be arranged to implement a voicesuppression technique, in which case even fewer packets would bereceived at the handset 1 from the headset 2.

It can be appreciated that using a combination of the above-describedmethods to reduce the number of empty voice packets transmitted andreceived optimises functioning of the handset 1. For example,implementing the detection system described above in the handset on itsown would be of significant benefit but if it were combined with the“further refinement” described above, even fewer packets would bereceived at the handset 1 from the headset 2. The handset 1 can be usedwith a standard Bluetooth headset. However, if the exemplary handset 1were used in conjunction with the headset 2 which was also implementingvoice suppression, even fewer packets would be received at the handset 1from the headset 2. (Once a call at the handset 1 using the headset 2 isactive the central arbitration unit 32 would not know in advance thatthe headset 2 would not be transmitting packets at certain times.However, the Bluetooth receive operation can be aborted quickly when theexpected packet header is not received, thereby allowing IEEE 802.11activity to be given a higher priority.) However, implementation of anyone or more of the techniques would be beneficial.

Ideally, the Bluetooth radio 60 would only suppress receiving andtransmission of voice packets when it would be likely to be ofsignificant benefit to the collocated IEEE 802.11 radio 40 so as tominimise disruption to normal Bluetooth transmission patterns and henceto minimise adverse affects on speech. Therefore, packets to be sent outfrom or received by the IEEE 802.11 radio portion 40 of the handset 1are also subject to arbitration in the central arbitration unit 32.

When information packets are received from the AP 4 via the aerial 30,they are received into the IEEE 802.11 transceiver 42. Instead ofpassing the information directly to the data processing unit 46, theinformation packets (or a part of the packets which enable the centralarbitration unit to analyse them) are passed to the central arbitrationunit 32. The central arbitration unit analyses the packets and uses theresults of the analysis to predict the content of future packets to bereceived. Although IEEE 802.11 packets which have already been receivedcan not be arbitrated, the central arbitration unit uses their nature orother related information to allocate a priority to future packetsdepending on the nature of the information carried by them. For example,if a received packet is VoIP, the central arbitration unit 32 can expectfurther similar packets and can decide to allocate those a high priorityand thereby prioritise them over Bluetooth packets that contain onlybackground noise. The exact arrival time of such packets can not beaccurately known because they must contend with other transmissions butthe central arbitration unit 32 can expect subsequent packets of amessage to arrive soon and can therefore set the transceiver 42 to beactive when such packets are expected. Similarly, the centralarbitration unit 32 knows that the AP 4 sends out regular beaconsproviding network maintenance information. These are scheduled to betransmitted at regular target times and thus the central arbitrationunit 32 can predict the timing of these packets. It might decide toallocate these a high priority and prioritise them over Bluetoothpackets that contain only background noise. If, on the other hand, thebeginning of a text, file or video data message is received, futurepackets could be allocated a medium priority. This is because such datacan be subjected to some delay but still be usable for the user of thehandset 1. Such a decision might also be based on the requiredthroughput of a message. Therefore, some future packets may not bereceived (because the aerial 30 is switched to Bluetooth) but in view ofthe voice analysis techniques described above, the chance ofsuccessfully receiving those packets when they are re-transmitted by theAP 4 (before the AP 4 has re-tried so many times the link is dropped),is significantly increased over the chance that a standard handset wouldhave.

Packets to be sent out by the IEEE 802.11 radio 40 can be arbitratedbefore being sent out and can be sent immediately or held whilstBluetooth activity occurs as appropriate.

Data packets allocated a high priority would be received and/ortransmitted immediately. Data packets allocated a medium priority wouldbe received or transmitted as quickly as possible but might be delayedfor a time where appropriate. For example, if the Bluetooth VAD unit 68has requested transmission of voice data to the headset 2 this wouldtake priority over the IEEE 802.11 data. However, because the inventionlimits the number of Bluetooth voice data packets transmitted to theheadset 2, during periods when the transceiver 62 has been instructednot to send out Bluetooth voice data packets, IEEE 802.11 data packetscan be safely transmitted or received without interference withBluetooth packets. Thus reception of a data message into the IEEE 802.11radio 40 of the handset 1 is completed far more quickly than in a priorart device in which reception of the packets forming the message wouldhave a much lower throughput. This is because, in view of the variousmeans described above, the IEEE 802.11 data is allocated a higherpriority than non-voice data-containing Bluetooth packets. Thus althoughsome buffering of the IEEE 802.11 data is still required, it is requiredto less of a degree and, in addition to allowing faster processing,errors in the IEEE 802.11 data are less likely as explained above.

If desired, the voice activity detection procedure can be disabled whenappropriate. In this embodiment no extra signalling need be used as thecentral arbitration unit 32 (or some other functional unit within theBluetooth transceiver 62) can determine the signal quality of the IEEE802.11 signals from received packets or other signals received on theIEEE 802.11 link. If the indicators of signal quality are such thatthere would be no benefit to implementing suppression of voice packets,then voice packets can be sent out at regular intervals in accordancewith the Bluetooth protocol as normal. This might be the case, forexample, if the signal on the IEEE 802.11 radio 40 is very strong incomparison to the voice link signal on the Bluetooth radio 60 and theantenna is not being shared via a switch, in which case it would beundesirable to risk disruption of the voice link. Equally, if the IEEE802.11 radio 40 is not in use, there is no need to implement any packetsuppression.

In this embodiment a storage device such as a memory for storinginformation and data on various types of signals is incorporated in thecentral arbitration unit 32. Such information relates to characteristicsof the signals such as interference patterns, minimum desirable signalstrengths, optimum operating frequencies etc. This information can beused to assist in determining whether there exists an interferencesituation which warrants implementation of voice activity detection andpacket suppression. The central arbitration unit 32 stores informationon the characteristics of the Bluetooth signals used by the handset 1.The received signal quality of the IEEE 802.11 is compared to thecharacteristics of Bluetooth signals which may or may not (depending onthe result of the comparison and their priority) be sent out. Thiscomparison enables the likelihood that the Bluetooth and IEEE 802.11signals might interfere with each other to be determined. The centralarbitration unit 32 can also store information on the characteristics ofIEEE 802.11 signals. In this case the comparison process can use thestored characteristics of the IEEE 802.11 signals to assist indetermining whether Bluetooth signals of a particular strength mightinterfere with a particular type of IEEE 802.11 data stream to be sentor received.

It is noted that comfort noise will need to be injected at both ends ofthe link when Bluetooth SCO packets are not transmitted (and thereforenot received) but this is the Bluetooth protocol's standard behaviour,as the Bluetooth protocol has to accommodate SCO packets that weretransmitted but lost due to propagation/interference issues. The qualityand intelligibility of speech would therefore not be significantlyaffected.

Thus it can be appreciated that embodiments of the invention improveIEEE 802.11 data throughput without reducing the intelligibility of aconcurrent Bluetooth voice link. Embodiments of the invention takeadvantage of more application-specific knowledge than is used byexisting coexistence schemes because of the ability to determine thepresence or likely presence of non-redundant information and alter theoperation of the radios as appropriate. This results in an overallbetter user experience than achieved with existing coexistencemechanisms.

When implementing the invention as described above, it is not necessaryfor all packets of the same type over a given time period to besubjected to the same treatment in accordance with allocated priorities.For example, in the situation where the central arbitration unitsimultaneously receives a request from the Bluetooth VAD unit 68 forvoice data to be transmitted to the headset 2 and a request from theIEEE 802.11 transceiver 42 to receive incoming data, although the voicedata is allocated a higher priority, it does not necessarily follow thatreceiving of the IEEE 802.11 data is completely stopped. Instead, thecentral arbitration unit 32 can decide not to receive IEEE 802.11packets for a duration of time and then decide to re-commence receptionand then stop reception again etc. Thus the number of IEEE 802.11packets received in a given longer timeframe (comprising several of thetime durations) can be reduced, thereby nevertheless reducing thelikelihood of interference during that timeframe. Similarly, instead ofceasing transmission of “empty” voice data packets between the handset 1and the headset 2 completely, fewer could be sent. In other words, thetechnique can be applied to a variable proportion of packets dependingon circumstances, including the number of packets in a message and thenumber of other packets which are expected to be received and/ortransmitted.

It can be understood by a person skilled in the art that theapplicability of the above-described embodiments is not limited to thehandset 1 and headset 2. Embodiments of the invention could be appliedto a handset similar to the handset 1 but having two aerials or a hybridaerial. Embodiments of the invention could be applied to other forms ofdevice such as PDAs and laptop computers. The embodiments could easilybe modified to work within other communications systems and otherprotocols. In particular, it is not necessary for the invention to beused within a Bluetooth system or with an IEEE 802.11 system. Theinvention could be applied to other radio protocols even if suchprotocols involved fewer or no empty voice data packets beingtransmitted in their standard form. The principles of the inventioncould nevertheless be applied to determine whether packets contain voicedata and/or to prioritise information packets between the radios. Theinvention is applicable to any two radios. One other radio system towhich the invention could be applied is Mobile WiMAX (IEEE 802.16e)which can interfere with, for example, a Bluetooth system. Another radiosystem to which the invention could be applied is ZigBee (IEEE 802.15.4)which can also interfere with, for example, a Bluetooth system.

The arrangement of components in the handset 1 could be varied. Onepossibility is that instead of, or in addition to, using a centralarbitration unit, each of the Bluetooth and IEEE 802.11 radios couldhave their own arbitration unit. In this case the two units would needto communicate priority information to each other to optimiseperformance of the device overall.

The decision as to whether packets containing only redundant informationshould be suppressed could be made by mechanisms other than signallingdifferent priorities to arbitration units. For example, the Bluetoothradio could be informed of the relative signal strengths (and hence thelikelihood of Bluetooth transmissions affecting IEEE 802.11 receptions)and the throughput requirements of IEEE 802.11 applications, and usesuch information to decide the proportion of “empty” packets containingonly redundant information or only background information that should besuppressed. Decisions could also be based on the type of data carried inpackets, the size of packets and the amount of data in packets. Anyuseful combination of the various types of information availableincluding the priority pre-assigned to a packet by a VAD or otheractivity detection device could be used to decide which informationpackets to receive and/or transmit.

The same technique could also be applied to combinations of othercommunications technologies that share a common medium, i.e. that sufferfrom a coexistence problem, especially where one of them is carrying avoice link. It is not essential for the invention to be used with avoice link, however. For example, the same technique could be used whena radio is engaged in data transfer. In this case, the radio could bealternatively or additionally provided with a different type ofinformation detection unit than a VAD unit. One example would be a radioengaged in receiving or transmitting the audio part of a video in whichcase a unit capable of detecting the presence of useful or non-redundantaudio data in a packet would be used.

The applicant hereby discloses in isolation each individual featuredescribed herein and any combination of two or more such features, tothe extent that such features or combinations are capable of beingcarried out based on the present specification as a whole in the lightof the common general knowledge of a person skilled in the art,irrespective of whether such features or combinations of features solveany problems disclosed herein, and without limitation to the scope ofthe claims. The applicant indicates that aspects of the presentinvention may consist of any such individual feature or combination offeatures. In view of the foregoing description it will be evident to aperson skilled in the art that various modifications may be made withinthe scope of the invention.

The invention claimed is:
 1. A radio apparatus comprising: a firsttransceiver means arranged to receive and transmit packets according toa first protocol; a second transceiver means arranged to receive ortransmit packets according to a second, different protocol, the secondtransceiver means being located such that interference is possiblebetween packets of the first and second protocols; a third transceivermeans arranged to receive packets; analyzing means for determining aprobability that a packet to be transmitted by the first transceivermeans does not contain only redundant information, and for determining aprobability that a packet to be received by the first transmitter meansdoes not contain only redundant information; and decision means formaking a respective decision based on a respective determinedprobability as to whether or not a packet to be transmitted should betransmitted and whether or not a packet to be received should bereceived, wherein the first transceiver means is arranged to transmit apacket that should be transmitted according to a respective decision,and to receive a packet that should be received according to arespective decision, and the analyzing means comprises an informationdetection means, arranged to detect the presence of non-redundantinformation in packets received at the third transceiver means, andwherein the analyzing means is arranged to determine the saidprobability in dependence on whether the presence of non-redundantinformation is detected in said packets received at the thirdtransceiver means or not.
 2. A radio apparatus according to claim 1,wherein the analyzing means is configured to determine a highprobability for a packet to be transmitted by the first transceivermeans and a low probability for a packet to be received by the firsttransceiver means if non-redundant information is detected in packetsreceived at the third transceiver means.
 3. A radio apparatus accordingto claim 1, wherein the analyzing means is configured to determine a lowprobability for a packet to be transmitted by the first transceivermeans and a high probability for a packet to be received by the firsttransceiver means if only redundant information is detected in packetsreceived at the third transceiver means.
 4. A radio apparatus accordingto claim 1, wherein the decision means is arranged to, if the determinedprobability that a packet to be transmitted or received by the firsttransceiver means does not contain only redundant information is high,make a decision that the packet should be received or transmitted.
 5. Aradio apparatus according to claim 1, wherein the decision means isarranged to, if the determined probability that a packet to betransmitted or received by the first transceiver means does not containonly redundant information is low, make a decision that the packetshould not be received or transmitted.
 6. A radio apparatus according toclaim 1, further comprising storing means for storing one or morecriteria defining whether information is redundant or non-redundant,wherein the analyzing means is arranged to determine the saidprobability that a packet to be transmitted or received by the firsttransceiver means does not contain only redundant information by meansof the stored one or more criteria.
 7. A radio apparatus according toclaim 1, wherein the information detection means comprises a voiceactivity detection means, arranged to detect the presence of voice datain packets received at the third transceiver means.
 8. A radio apparatusaccording to claim 7, wherein the analyzing means is further arranged todetermine the said probability that a packet to be transmitted orreceived by the first transceiver means does not contain only redundantinformation in dependence on whether the presence of voice data isdetected or not.
 9. A radio apparatus according to claim 8, wherein theanalyzing means is arranged to determine a high probability for a packetto be transmitted by the first transceiver means and a low probabilityfor a packet to be received by the first transceiver means if voice datais detected in packets received at the third transceiver means.
 10. Aradio apparatus according to claim 8, wherein the analyzing means isarranged to determine a low probability for a packet to be transmittedby the first transceiver means and a high probability for a packet to bereceived by the first transceiver means if no voice data is detected inpackets received at the third transceiver means.
 11. A radio apparatusaccording to claim 1, wherein the information detection means comprisesa non-voice audio activity detection means, arranged to detect thepresence of non-voice audio data in packets received at the thirdtransceiver means and wherein the analyzing means is further arranged todetermine the said probability in dependence on whether the presence ofnon-voice audio data is detected or not and to thereby determine a highprobability for a packet to be transmitted and a low probability for apacket to be received if non-voice audio data is detected and a lowprobability for a packet to be transmitted and a high probability for apacket to be received if no non-voice audio data is detected.
 12. Aradio apparatus according to claim 1, wherein the information detectionmeans is further arranged to detect the absence of packets at the thirdtransceiver means and to thereby determine a low probability for apacket to be transmitted by the first transceiver means if an absence isdetected.
 13. A radio apparatus according to claim 1, wherein the thirdtransceiver means is different from the second transceiver means and isarranged to receive packets according to a third protocol.
 14. A radioapparatus according to claim 1, wherein the decision means comprises anarbitration means, arranged to receive notification of the determinedprobability that a packet to be transmitted or received by the firsttransceiver means does not contain only redundant information from theanalyzing means and to allocate a transmission or receiving priority toa packet based on said determined probability and wherein the decisionmeans is further arranged to make the said decision based on theallocated priority.
 15. A radio apparatus according to claim 14, whereinthe second transceiver means is further arranged to request thearbitration means to allocate a transmitting or receiving priority topackets, and wherein the arbitration means is arranged to allocate atransmitting or receiving priority to the said packets based ontransmission and receiving priorities of other packets.
 16. A radioapparatus according to claim 14, wherein the arbitration means isfurther arranged to inform the second transceiver means of thetransmission or receiving priority of packets and wherein the secondtransceiver means is further arranged to respectively transmit orreceive packets according to their allocated priority.
 17. A radioapparatus according to claim 14, wherein the analyzing means is furtherarranged to request the arbitration means to allocate a transmission orreceiving priority to a packet, and wherein the arbitration means isarranged to allocate a priority to the said packet based on transmissionor receiving priorities of other packets.
 18. A radio apparatusaccording to claim 14, wherein the arbitration means is further arrangedto allocate receiving and transmission priorities of packets based onother information including at least one of: type of data carried inpacket; size of packet; amount of data in packet; signal strengths inthe first and second protocols; throughput requirement of message ofwhich the packet forms a part; number of packets of the message of whichthe packet forms part; number of packets awaiting reception and/ortransmission; processing or transmission status of previously-receivedpackets; position of packet in a message; and priority pre-assigned topacket.
 19. A radio apparatus according to claim 1, wherein the secondtransceiver means is additionally for determining an indication of asignal quality of packets received according to the second protocol andwherein the radio apparatus further comprises: storing means for storinginformation relating to characteristics of signals of the firstprotocol; and comparing means for comparing the said indication to thestored information to determine a likelihood of interference betweensignals of the first and second protocols, and wherein the decisionmeans is additionally for making the said decision based on thedetermined likelihood.
 20. A radio apparatus according to claim 19,wherein the storing means is further for storing further informationrelating to characteristics of signals of the second protocol andwherein the comparing means is additionally for determining thelikelihood of interference based on the stored further information. 21.A radio apparatus according to claim 19, wherein the stored informationand further information comprise one or more of: minimum desirablesignal strengths; modeled interference behavior of the first and secondradio signals; and working frequency ranges of the first and secondradio signals.
 22. A radio apparatus according to claim 19, wherein thedecision means is arranged to, if the determined indication is below apredetermined threshold, cause the analyzing means not to be used.
 23. Aradio apparatus according to claim 1, further comprising: a first localarbitration means associated with the first transceiver means andarranged to allocate receiving and/or transmission priorities to packetsof the first protocol; and a second local arbitration means associatedwith the second transceiver means and arranged to allocate receivingand/or transmission priorities to packets of the second protocol,wherein the first and second arbitration means are arranged to informeach other of allocated priorities.
 24. A radio apparatus according toclaim 1, further comprising an antenna means for receiving packets fromthe first and second transceiver means and arranged to transmit saidpackets, and wherein the first and second transceiver means are arrangedto send packets to the antenna means according to priorities of packetsand/or said decision.
 25. A radio apparatus according to claim 1,wherein the decision means is arranged to, if no real-time data is beingreceived or transmitted according to the second protocol, cause theanalyzing means not to be used.
 26. A method of reducing interferencebetween a first and a second transceiver located in a radio apparatus,the first transceiver being operable to receive and transmit packetsaccording to a first protocol and the second transceiver being operableto receive or transmit packets according to a second, differentprotocol, the method comprising the steps of: determining a probabilitythat a packet to be transmitted by the first radio apparatus does notcontain only redundant information; determining a probability that apacket to be received by the first radio apparatus does not contain onlyredundant information; making a respective decision based on arespective determined probability as to whether or not a packet to betransmitted should be transmitted and whether or not a packet to bereceived should be received; and transmitting a packet that should betransmitted according to a respective decision, and receiving a packetthat should be received according to a respective decision, wherein theprobability is determined in dependence on whether the presence ofnon-redundant information is detected in packets received at a thirdtransceiver means or not.